The metabolism of organic substrates and production of H2O2, a potenti
al pathogenicity factor, were studied in the type strains of fourteen
avian Mycoplasma species, and in low-passage isolates of M. gallinarum
, M. gallisepticum, M. iners and M. pullorum. Substrates were added to
cell suspensions in Ringer or saline solution and oxygen uptake and/o
r change in pH monitored, The fermentative species could be sub-divide
d according to whether O-2 uptake did (M. anatis, M. columborale, M. g
allisepticum, M. imitans and M. iowae) or did not (M. gallinaceum, M.
gallopavonis and M. pullorum) accompany glucose metabolism and the fiv
e non-fermentative, arginine-hydrolysing strains according to whether
organic acids (lactate, 2-oxobutyrate, pyruvate) were (M. columbinasal
e, M. columbinum and M. gallinarum) or were not (M. iners and M. melea
gridis) oxidized. Lysed cells of strains which consumed O-2 during glu
cose or organic acid metabolism had relatively high NADH oxidase activ
ity (170-950 nmol min(-1) mg cell protein(-1)) and produced 0.02-0.36
mol H2O2 per mol O-2 consumed during NADH oxidation, In contrast, stra
ins which did not oxidize organic acids or consume O-2 during glucose
or organic acid metabolism possessed low NADH oxidase activity (less t
han or equal to 20 nmol min(-1) mg cell protein(-1)), All arginine-hyd
rolysing species showed a high affinity (Km value 1-3 mu M) towards ar
ginine, The fermentative species similarly showed a high affinity (Km
value 2-5 mu M) towards glucose, but used only a small number of addit
ional sugars at detectable rates. All M. pullorum strains metabolized
sucrose (Km less than or equal to 3 mu M) The type-strains of M. galli
septicum and M. imitans were biochemically similar and had high affini
ties for fructose and mannose. A number of low-passage avian isolates,
but none of the type strains, metabolized glycerol and, in lysed cell
s, oxidized L-alpha-glycerophosphate (GP) with the production of 1 mol
H2O2 per mol GP.